Inflammatory diet linked to CRC risk

medwireNews: A diet rich in foods with a high inflammatory potential is associated with a significant increase in the risk for colorectal cancer (CRC), say US researchers who collated information from more than 120,000 adults followed up over 26 years.

An empirical dietary inflammatory pattern (EDIP) score was applied to food frequency questionnaire responses taken from the Health Professionals Follow-up Study and the Nurses’ Health Study, both of which concluded in 2012.

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The EDIP score was previously devised to classify 18 food groups by their relationship to the plasma inflammatory markers interleukin-6, C-reactive protein, and the tumor necrosis factor receptor superfamily 1B, explain Fred Tabung, from Harvard TH Chan School of Public Health in Boston, Massachusetts, and co-workers.

Anti-inflammatory food stuffs included beer, wine, tea, and dark yellow and green leafy vegetables, whereas intake of processed and red meat, other vegetables, refined grains and tomatoes was shown to be positively correlated with inflammatory markers.

Over 2,571,831 person–years of follow-up, 2699 patients were diagnosed with CRC.

Men and women in the lowest quintile for EDIP score had a CRC incidence of 113 and 80 cases per 100,000 person–years, respectively, versus an incidence of 151 and 92 cases for those in the highest EDIP quintile.

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Multivariate analysis confirmed that a higher EDIP score was associated with a significantly greater risk for CRC for both men (hazard ratio [HR]=1.44) and women (HR=1.22), giving a pooled HR of 1.32.

This was true for diagnoses sited in the entire colon, proximal colon, and distal colon for both men and women, although only men had an increased risk for rectal cancer, a finding that the researchers believe is “unlikely to be due to chance given the large significant heterogeneity by sex.”

Further analysis found that the relationship between EDIP score and CRC risk was modified by alcohol intake. Among men and women who did not consume alcohol, those in the highest versus lowest EDIP quintile had a 62% and 33% increased risk for CRC, respectively. But this was attenuated to 23% for men who consumed at least one drink per day, and the association between the EDIP quintile and CRC risk was no longer significant for women who consumed alcohol.

“It is possible that the adverse effects of alcohol intake through other mechanisms may be more dominant than those of its effect on the EDIP and may partially explain the stronger associations among men and women not consuming alcohol than among alcohol consumers,” the researchers postulate.

Similarly, for men in the fifth versus first EDIP quintile, those with a body mass index indicating overweight or obesity had a greater increased risk for CRC than those with a healthy weight (HR=1.48 vs 1.39), but women with a healthy weight had a greater risk than their overweight or obese counterparts (HR=1.31 vs 1.11).

Tabung et al therefore suggest in JAMA Oncology: “Strategies to reduce the adverse role of a proinflammatory dietary pattern in colorectal cancer development may have higher benefits among overweight or obese men and among lean women or among men and women not consuming alcohol.”